I know this was brought up a while back Scott did anyone ever find out what was causing it? I use tip tac for my tool tips so im gonna turn that off and run something when I get a chance. I know with it enabled it seems like the hit box for the item in the group loot frame is being covered by something because I can get it to show sometimes if I move my mouse around the edges but its a pain in the ass. For now if I loot the corpse my self the tooltip will appear in my loot frame so its not the end of the world. If you need to know anything else lemme know.

I would suggest using the MouseFocus script to see what the invisible frame is. nUI does not modify the group loot other than to move its location, so there should be no nUI frame that interferes with the mouseover on it.

Not sure what the issue would be.

Just make a macro to execute the following and key bind it -- when the problem happens, put the mouse over the dead area and run the macro. It will tell you the name of the frame that's causing the problem. Hopefully that will give us a hint what the problem is.